Stability of the ternary perovskites ${\text{Sc}}_{3}E\text{N}$ $\left(E=\text{B},\text{Al},\text{Ga},\text{In}\right)$ from first principles

Mechanical and thermodynamic stability of the isoelectronic ternary inverse perovskites ${\text{Sc}}_3\text{EN}$ $\left(E=\text{B},\text{Al},\text{Ga},\text{In}\right)$ has been studied from first principles. We confirm stability of recently synthesized cubic phases ${\text{Sc}}_3\text{AlN}$ and ${\text{Sc}}_3\text{InN}$, and predict the stability of cubic ${\text{Sc}}_3\text{GaN}$ and a triclinic phase aP20-${\text{Sc}}_3\text{BN}$. Substantial phonon softening in ${\text{Sc}}_3\text{AlN}$ and ${\text{Sc}}_3\text{GaN}$ is observed indicating a possibility that structural defects could form readily. In accord, our experiments show that magnetron sputter deposited films contain regions with high density of nonperiodic stacking faults along the $⟨111⟩$ growth direction. We suggest that defect-free crystals may exhibit anomalies in the carrier properties, promising for electronic applications.

Figure 1

(Color online) Crystal structure of the cubic inverse ${\text{Sc}}_3\text{AlN}$ perovskite. Sc, Al, and N are marked by green (the largest circle), blue (the medium-sized circle), and red (the smallest circle) colors, respectively.

Figure 2

Stabilization enthalpy [Eq. (1)] of cubic ${\text{Sc}}_{3}E\text{N}$ ($E=\text{B}$, Al, Ga, and In) perovskite compounds.

Figure 3

Phonon spectra of (a) ${\text{Sc}}_3\text{BN}$, (b) ${\text{Sc}}_3\text{AlN}$, (c) ${\text{Sc}}_3\text{GaN}$, and (d) ${\text{Sc}}_3\text{InN}$. Negative values in (a) indicate imaginary frequencies.

Figure 4

(Color online) Crystal structures of ${\text{Sc}}_3\text{BN}$: $T\text{−}10$ (a), $R\text{−}10$ (b), and Tryck-20 (c). Blue atoms: B; green atoms: Sc; and red atoms: N.

Figure 5

(Color online) Electronic density of states (DOS) of cubic ${\text{Sc}}_{3}E\text{N}$ $\left(E=\text{Al},\text{Ga},\text{In}\right)$ and Tryck-20 ${\text{Sc}}_3\text{BN}$. The values of DOS for different compounds are shifted.

Figure 6

(Color online) Band structure and partial DOS of ${\text{Sc}}_3\text{AlN}$

Figure 7

XTEM images from a ${\text{Sc}}_3\text{AlN}\left(111\right)$ film sputter deposited on a ScN(111) seed layer on MgO(111) substrate (not shown). (a) The overview (the dash line shows the interface between seed layer and ${\text{Sc}}_3\text{AlN}$), (b) a higher magnification (the arrow depicts a dislocation), and (c) selected area electron-diffraction pattern.